Method of producing cathode materials



Patented Sept. 17, 1940 METHOD OF PRODUCING CATHODE MATERIALS FelixHerriger, Berlin, Germany, assignor to G. Lorenz Aktiengesellschaft,Berlin-Tempelhof,

Germany, a company No Drawing. Application December 27, 1939, Se-

rial No. 311,136. In Germany December 2,

3 Claims.

This invention relates to methods of producing cathode materials andconsists in certain features of novelty which will be readily understoodfrom the following and be pointed out in the ap- 5 pended claims.

It is a known fact that the electron emissive performance of thoriatedtungsten cathodes on account of the absorbed mono-atomic molecular layerof thorium is lower than if the cathode is made of pure tungsten. It isalso familiar to those skilled in the art that even thoriated tantalumcathodes do not give any increase with respect to the electron emissionperformance since the two elements thorium and tantalum are classifiedin the same group or family of the periodic system, from which followsthat the dipole momentum, which inherently contributes toward areduction of the electron emission performance, assumes a very lowvalue.

Careful investigations made by applicant have proven that the dipolemomentum still-may be increased. This is accomplished according to thisinvention by replacing the bearing cathode element tungsten by rheniumwhich also possesses a very high melting point. The dipole momentumbetween the elements thorium and rhenium is considerably higher thanbetween thorium and tungsten, so that the electron emission performanceis proportionately reduced. This 30 effect is causitive to theclassification of thorium and rhenium in the periodic system.

Although the rhenium does not form any carbide, it involves such highabsorption properties with respect to thorium that no appreciableevaporation of the thorium from its superficies will take place atnormal operating temperatures of say 1800 degrees centigrade.

The manufacture of thoriated rhenium cath- 5 odes is similar to that ofthoriated tungsten cathodes. To the metallic rhenium powder there isadded up to 10 per cent of powdered rhenium oxide. This mixture is firstcompressed at a high pressure and then sintered in a protective gase- 10ous atmosphere, whereupon the resulting blocks are hammered to thedesirable shape and size.

What is claimed is:

1. The method of producing cathode materials which comprises mixingmetallic rhenium pow- 15 der and an additional amount up to 10 per centof pulverized thorium oxide, compressing the resulting mixture at highpressure, and sintering the compressed compound in a protective gaseousatmosphere. 20

2. The method of producing cathodes for electron discharge devices whichcomprises mixing metallic rhenium powder and an additional amount of upto 10-per cent of pulverized thorium oxide, compressing this mixture athigh pressure, sintering the compressed compound in a protective gaseousatmosphere, and hammering the resulting blocks to the desirable shapeand size.

3. As a product of manufacture, a cathode for electron discharge devicesconsisting of rhenium and an additional amount of up to 10 per cent ofthorium.

FELIX HERRIGER.

